I also had trouble with the filter wheel when I first got it. It would turn by some random amount and end up blocking te CCDS. No amount of tightening seemed to work. I ended up sending it to SBIG. What ever they did has worked perfectly for the past two years. BTW turning the filter wheel over will result in scratched filters, because I'ved tried that.

Thanks for the comments. The photometric filter wheel was on correctly (with the filters up), but the screw was a little loose. It seems to be working now.

When I purchased the camera the filter wheel was packaged separately. The washer that was on the shutter wheel would not work with the filter wheel. I think this was because the two wheels have different thicknesses. I experimented with different washers and found one to work with the filter wheel.

Hopefully it wil remain okay now, but if not I might follow Jeff's lead and send mine back to SBIG.